var LEVELS = [
				[
					"                                                                                ",
					"                                                                                ",
					"                                                                                ",
					"                                                                                ",
					"                                                                                ",
					"                                                                                ",
					"                                                                  xxx           ",
					"                                                   xx      xx    xx!xx          ",
					"                                    o o      xx                  x!!!x          ",
					"                                                                 xx!xx          ",
					"                                   xxxxx                          xvx           ",
					"                                                                            xx  ",
					"  xx                                      o o                                x  ",
					"  x                     o                                                    x  ",
					"  x                                      xxxxx                             o x  ",
					"  x          xxxx       o                                                    x  ",
					"  x  @       x  x                                                xxxxx       x  ",
					"  xxxxxxxxxxxx  xxxxxxxxxxxxxxx   xxxxxxxxxxxxxxxxxxxx     xxxxxxx   xxxxxxxxx  ",
					"                              x   x                  x     x                    ",
					"                              x!!!x                  x!!!!!x                    ",
					"                              x!!!x                  x!!!!!x                    ",
					"                              xxxxx                  xxxxxxx                    ",
					"                                                                                ",
					"                                                                                "
				],
				[
					"                                      x!!x                        xxxxxxx                                    x!x  ",
					"                                      x!!x                     xxxx     xxxx                                 x!x  ",
					"                                      x!!xxxxxxxxxx           xx           xx                                x!x  ",
					"                                      xx!!!!!!!!!!xx         xx             xx                               x!x  ",
					"                                       xxxxxxxxxx!!x         x                                    o   o   o  x!x  ",
					"                                                xx!x         x     o   o                                    xx!x  ",
					"                                                 x!x         x                                xxxxxxxxxxxxxxx!!x  ",
					"                                                 xvx         x     x   x                        !!!!!!!!!!!!!!xx  ",
					"                                                             xx  |   |   |  xx            xxxxxxxxxxxxxxxxxxxxx   ",
					"                                                              xx!!!!!!!!!!!xx            v                        ",
					"                                                               xxxx!!!!!xxxx                                      ",
					"                                               x     x            xxxxxxx        xxx         xxx                  ",
					"                                               x     x                           x x         x x                  ",
					"                                               x     x                             x         x                    ",
					"                                               x     x                             xx        x                    ",
					"                                               xx    x                             x         x                    ",
					"                                               x     x      o  o     x   x         x         x                    ",
					"               xxxxxxx        xxx   xxx        x     x               x   x         x         x                    ",
					"              xx     xx         x   x          x     x     xxxxxx    x   x   xxxxxxxxx       x                    ",
					"             xx       xx        x o x          x    xx               x   x   x               x                    ",
					"     @       x         x        x   x          x     x               x   x   x               x                    ",
					"    xxx      x         x        x   x          x     x               x   xxxxx   xxxxxx      x                    ",
					"    x x      x         x       xx o xx         x     x               x     o     x x         x                    ",
					"!!!!x x!!!!!!x         x!!!!!!xx     xx!!!!!!!!xx    x!!!!!!!!!!     x     =     x x         x                    ",
					"!!!!x x!!!!!!x         x!!!!!xx       xxxxxxxxxx     x!!!!!!!xx!     xxxxxxxxxxxxx xx  o o  xx                    ",
					"!!!!x x!!!!!!x         x!!!!!x    o                 xx!!!!!!xx !                    xx     xx                     ",
					"!!!!x x!!!!!!x         x!!!!!x                     xx!!!!!!xx  !                     xxxxxxx                      ",
					"!!!!x x!!!!!!x         x!!!!!xx       xxxxxxxxxxxxxx!!!!!!xx   !                                                  ",
					"!!!!x x!!!!!!x         x!!!!!!xxxxxxxxx!!!!!!!!!!!!!!!!!!xx    !                                                  ",
					"!!!!x x!!!!!!x         x!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!xx     !                                                  "
				],
				[
					"                                                                                                              ",
					"                                                                                                              ",
					"                                                                                                              ",
					"                                                                                                              ",
					"                                                                                                              ",
					"                                        o                                                                     ",
					"                                                                                                              ",
					"                                        x                                                                     ",
					"                                        x                                                                     ",
					"                                        x                                                                     ",
					"                                        x                                                                     ",
					"                                       xxx                                                                    ",
					"                                       x x                 !!!        !!!  xxx                                ",
					"                                       x x                 !x!        !x!                                     ",
					"                                     xxx xxx                x          x                                      ",
					"                                      x   x                 x   oooo   x       xxx                            ",
					"                                      x   x                 x          x      x!!!x                           ",
					"                                      x   x                 xxxxxxxxxxxx       xxx                            ",
					"                                     xx   xx      x   x      x                                                ",
					"                                      x   xxxxxxxxx   xxxxxxxx              x x                               ",
					"                                      x   x           x                    x!!!x                              ",
					"                                      x   x           x                     xxx                               ",
					"                                     xx   xx          x                                                       ",
					"                                      x   x= = = =    x            xxx                                        ",
					"                                      x   x           x           x!!!x                                       ",
					"                                      x   x    = = = =x     o      xxx       xxx                              ",
					"                                     xx   xx          x                     x!!!x                             ",
					"                              o   o   x   x           x     x                xxv        xxx                   ",
					"                                      x   x           x              x                 x!!!x                  ",
					"                             xxx xxx xxx xxx     o o  x!!!!!!!!!!!!!!x                   vx                   ",
					"                             x xxx x x xxx x          x!!!!!!!!!!!!!!x                                        ",
					"                             x             x   xxxxxxxxxxxxxxxxxxxxxxx                                        ",
					"                             xx           xx                                         xxx                      ",
					"  xxx                         x     x     x                                         x!!!x                xxx  ",
					"  x x                         x    xxx    x                                          xxx                 x x  ",
					"  x                           x    xxx    xxxxxxx                        xxxxx                             x  ",
					"  x                           x           x                              x   x                             x  ",
					"  x                           xx          x                              x x x                             x  ",
					"  x                                       x       |xxxx|    |xxxx|     xxx xxx                             x  ",
					"  x                xxx             o o    x                              x         xxx                     x  ",
					"  x               xxxxx       xx          x                             xxx       x!!!x          x         x  ",
					"  x               oxxxo       x    xxx    x                             x x        xxx          xxx        x  ",
					"  x                xxx        xxxxxxxxxxxxx  x oo x    x oo x    x oo  xx xx                    xxx        x  ",
					"  x      @          x         x           x!!x    x!!!!x    x!!!!x    xx   xx                    x         x  ",
					"  xxxxxxxxxxxxxxxxxxxxxxxxxxxxx           xxxxxxxxxxxxxxxxxxxxxxxxxxxxx     xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx  ",
					"                                                                                                              ",
					"                                                                                                              "
				],
				[
					"                                                                                                  xxx x       ",
					"                                                                                                      x       ",
					"                                                                                                  xxxxx       ",
					"                                                                                                  x           ",
					"                                                                                                  x xxx       ",
					"                          o                                                                       x x x       ",
					"                                                                                             o o oxxx x       ",
					"                   xxx                                                                                x       ",
					"       !  o  !                                                xxxxx xxxxx xxxxx xxxxx xxxxx xxxxx xxxxx       ",
					"       x     x                                                x   x x   x x   x x   x x   x x   x x           ",
					"       x= o  x            x                                   xxx x xxx x xxx x xxx x xxx x xxx x xxxxx       ",
					"       x     x                                                  x x   x x   x x   x x   x x   x x     x       ",
					"       !  o  !            o                                  xxxx xxxxx xxxxx xxxxx xxxxx xxxxx xxxxxxx       ",
					"                                                                                                              ",
					"          o              xxx                              xx                                                  ",
					"                                                                                                              ",
					"                                                                                                              ",
					"                                                      xx                                                      ",
					"                   xxx         xxx                                                                            ",
					"                                                                                                              ",
					"                          o                                                     x      x                      ",
					"                                                          xx     xx                                           ",
					"             xxx         xxx         xxx                                 x                  x                 ",
					"                                                                                                              ",
					"                                                                 ||                                           ",
					"  xxxxxxxxxxx                                                                                                 ",
					"  x         x o xxxxxxxxx o xxxxxxxxx o xx                                                x                   ",
					"  x         x   x       x   x       x   x                 ||                  x     x                         ",
					"  x  @      xxxxx   o   xxxxx   o   xxxxx                                                                     ",
					"  xxxxxxx                                     xxxxx       xx     xx     xxx                                   ",
					"        x=                  =                =x   x                     xxx                                   ",
					"        xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx   x!!!!!!!!!!!!!!!!!!!!!xxx!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!",
					"                                                  xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx",
					"                                                                                                              "
				]
			];
			
			function Vector(x, y) {
				this.x = x;
				this.y = y;
			}
			
			Vector.prototype.plus = function (other) {
				return new Vector(this.x + other.x, this.y + other.y);
			};
			
			Vector.prototype.times = function (scale) {
				return new Vector(this.x * scale, this.y * scale);
			};
			
			// 注意：使用大写单词表示构造函数是值
			var actorchars = {
				"@": Player,
				o: Coin,
				"=": Lava,
				"|": Lava,
				v: Lava
			};
			
			function Player(pos) {
				this.pos = pos.plus(new Vector(0, -0.5));
				this.size = new Vector(0.5, 1);
				this.speed = new Vector(0, 0);
			}
			Player.prototype.type = "player";
			
			function Lava(pos, ch) {
				this.pos = pos;
				this.size = new Vector(1, 1);
				if (ch === "=") this.speed = new Vector(2, 0);
				else if (ch === "|") this.speed = new Vector(0, 2);
				else if (ch === "v") {
					this.speed = new Vector(0, 3);
					this.repeatPos = pos;
				}
			}
			Lava.prototype.type = "Lava";
			
			function Coin(pos) {
				this.basePos = this.pos = pos;
				this.size = new Vector(0.6, 0.6);
				// 回头看看
				this.wobble = Math.random() * Math.PI * 2;
			}
			Coin.prototype.type = "coin";
			
			Level.prototype.isFinished = function () {
				return this.status != null && this.finishDelay < 0;
			};
			
			function Level(plan) {
				this.width = plan[0].length;
				this.height = plan.length;
				this.grid = [];
				this.actors = [];
			
				for (var y = 0; y < this.height; y++) {
					var line = plan[y],
						gridLine = [];
					for (var x = 0; x < this.width; x++) {
						var ch = line[x],
							fieldType = null;
						var Actor = actorchars[ch];
						if (Actor) this.actors.push(new Actor(new Vector(x, y), ch));
						else if (ch === "x") fieldType = "wall";
						else if (ch === "!") fieldType = "lava";
						else if (ch === "|") fieldType = "lava";
						else if (ch === "=") fieldType = "lava";
						else if (ch === "v") {
							fieldType = "lava";
							console.log(fieldType);
						}
						gridLine.push(fieldType);
					}
					this.grid.push(gridLine);
				}
				this.player = this.actors.filter(function (actor) {
					return actor.type === "player";
				})[0];
				this.status = this.finishDelay = null;
			}
			
			function element(name, className) {
				var elem = document.createElement(name);
				if (className) elem.className = className;
				return elem;
			}
			
			function DOMDisplay(parent, level) {
				this.wrap = parent.appendChild(element("div", "game"));
				this.level = level;
			
				this.wrap.appendChild(this.drawBackground());
				this.actorLayer = null;
				this.drawFrame();
			}
			
			var scale = 15;
			
			DOMDisplay.prototype.drawBackground = function () {
				var table = element("table", "background");
				table.style.width = this.level.width * scale + "px";
				table.style.height = this.level.height * scale + "px";
				this.level.grid.forEach(function (row) {
					var rowElement = table.appendChild(element("tr"));
					rowElement.style.height = scale + "px";
					row.forEach(function (type) {
						rowElement.appendChild(element("td", type));
					});
				});
				return table;
			};
			
			DOMDisplay.prototype.drawActors = function () {
				var wrap = element("div");
				this.level.actors.forEach(function (actor) {
					var rect = wrap.appendChild(element("div", "actor " + actor.type));
					rect.style.width = actor.size.x * scale + "px";
					rect.style.height = actor.size.y * scale + "px";
					rect.style.left = actor.pos.x * scale + "px";
					rect.style.top = actor.pos.y * scale + "px";
				});
				return wrap;
			};
			
			DOMDisplay.prototype.drawFrame = function () {
				if (this.actorLayer) this.wrap.removeChild(this.actorLayer);
				this.actorLayer = this.wrap.appendChild(this.drawActors());
				this.wrap.className = "game " + (this.level.status || "");
				this.scrollPlayerIntoView();
			};
			
			// 稍后清除
			DOMDisplay.prototype.scrollPlayerIntoView = function () {
				var width = this.wrap.clientWidth;
				var height = this.wrap.clientHeight;
				var margin = width / 3;
			
				// The viewport
				var left = this.wrap.scrollLeft,
					right = left + width;
				var top = this.wrap.scrollTop,
					bottom = top + height;
			
				var player = this.level.player;
				var center = player.pos.plus(player.size.times(0.5)).times(scale);
			
				if (center.x < left + margin) this.wrap.scrollLeft = center.x - margin;
				else if (center.x > right - margin)
					this.wrap.scrollLeft = center.x + margin - width;
				if (center.y < top + margin) this.wrap.scrollTop = center.y - margin;
				else if (center.y > bottom - margin)
					this.wrap.scrollTop = center.y + margin - height;
			};
			
			DOMDisplay.prototype.clear = function () {
				this.wrap.parentNode.removeChild(this.wrap);
			};
			
			Level.prototype.obstacleAt = function (pos, size) {
				var xStart = Math.floor(pos.x);
				var xEnd = Math.ceil(pos.x + size.x);
				var yStart = Math.floor(pos.y);
				var yEnd = Math.ceil(pos.y + size.y);
			
				if (xStart < 0 || xEnd > this.width || yStart < 0) return "wall";
				if (yEnd > this.height) return "lava";
				for (var y = yStart; y < yEnd; y++) {
					for (var x = xStart; x < xEnd; x++) {
						var fieldType = this.grid[y][x];
						if (fieldType) return fieldType;
					}
				}
			};
			
			Level.prototype.actorAt = function (actor) {
				for (var i = 0; i < this.actors.length; i++) {
					var other = this.actors[i];
					if (
						other != actor &&
						actor.pos.x + actor.size.x > other.pos.x &&
						actor.pos.x < other.pos.x + other.size.x &&
						actor.pos.y + actor.size.y > other.pos.y &&
						actor.pos.y < other.pos.y + other.size.y
					)
						return other;
				}
			};
			
			var maxStep = 0.05;
			
			Level.prototype.animate = function (step, keys) {
				if (this.status != null) this.finishDelay -= step;
			
				while (step > 0) {
					var thisStep = Math.min(step, maxStep);
					this.actors.forEach(function (actor) {
						actor.act(thisStep, this, keys);
					}, this);
					step -= thisStep;
				}
			};
			
			Lava.prototype.act = function (step, level) {
				var newPos = this.pos.plus(this.speed.times(step));
				if (!level.obstacleAt(newPos, this.size)) this.pos = newPos;
				else if (this.repeatPos) this.pos = this.repeatPos;
				else this.speed = this.speed.times(-1);
			};
			
			var wobbleSpeed = 8,
				wobbleDist = 0.07;
			
			Coin.prototype.act = function (step) {
				this.wobble += step * wobbleSpeed;
				var wobblePos = Math.sin(this.wobble) * wobbleDist;
				this.pos = this.basePos.plus(new Vector(0, wobblePos));
			};
			
			var playerXSpeed = 10;
			
			Player.prototype.moveX = function (step, level, keys) {
				this.speed.x = 0;
				if (keys.left) this.speed.x -= playerXSpeed;
				if (keys.right) this.speed.x += playerXSpeed;
			
				var motion = new Vector(this.speed.x * step, 0);
				var newPos = this.pos.plus(motion);
				var obstacle = level.obstacleAt(newPos, this.size);
				if (obstacle) level.playerTouched(obstacle);
				else this.pos = newPos;
			};
			
			var gravity = 30;
			var jumpSpeed = 17;
			
			Player.prototype.moveY = function (step, level, keys) {
				this.speed.y += step * gravity;
				var motion = new Vector(0, this.speed.y * step);
				var newPos = this.pos.plus(motion);
				var obstacle = level.obstacleAt(newPos, this.size);
				if (obstacle) {
					level.playerTouched(obstacle);
					if (keys.up && this.speed.y > 0) this.speed.y = -jumpSpeed;
					else this.speed.y = 0;
				} else {
					this.pos = newPos;
				}
			};
			
			Player.prototype.act = function (step, level, keys) {
				this.moveX(step, level, keys);
				this.moveY(step, level, keys);
			
				var otherActor = level.actorAt(this);
				if (otherActor) level.playerTouched(otherActor.type, otherActor);
			
				// 丢失动画
				if (level.status == "lost") {
					this.pos.y += step;
					this.size.y -= step;
				}
			};
			
			Level.prototype.playerTouched = function (type, actor) {
				if (type == "lava" && this.status == null) {
					this.status = "lost";
					this.finishDelay = 1;
				} else if (type == "coin") {
					this.actors = this.actors.filter(function (other) {
						return other != actor;
					});
					if (
						!this.actors.some(function (actor) {
							return actor.type == "coin";
						})
					) {
						this.status = "won";
						this.finishDelay = 1;
					}
				}
			};
			
			var arrowCodes = { 37: "left", 38: "up", 39: "right" };
			
			function trackKeys(codes) {
				var pressed = Object.create(null);
				function handler(event) {
					if (codes.hasOwnProperty(event.keyCode)) {
						var down = event.type == "keydown";
						pressed[codes[event.keyCode]] = down;
						event.preventDefault();
					}
				}
				addEventListener("keydown", handler);
				addEventListener("keyup", handler);
				return pressed;
			}
			
			function runAnimation(frameFunc) {
				var lastTime = null;
				function frame(time) {
					var stop = false;
					if (lastTime != null) {
						var timeStep = Math.min(time - lastTime, 100) / 1000;
						stop = frameFunc(timeStep) === false;
					}
					lastTime = time;
					if (!stop) requestAnimationFrame(frame);
				}
				requestAnimationFrame(frame);
			}
			
			var arrows = trackKeys(arrowCodes);
			
			function runLevel(level, Display, andThen) {
				var display = new Display(document.body, level);
				runAnimation(function (step) {
					level.animate(step, arrows);
					display.drawFrame(step);
					if (level.isFinished()) {
						display.clear();
						if (andThen) andThen(level.status);
						return false;
					}
				});
			}
			
			function runGame(plans, Display) {
				function startLevel(n) {
					runLevel(new Level(plans[n]), Display, function (status) {
						if (status == "lost") startLevel(n);
						else if (n < plans.length - 1) startLevel(n + 1);
						else alert("You win!");
					});
				}
				startLevel(0);
			}
			
			runGame(LEVELS, DOMDisplay);